Solid electrolyte material and solid-state battery made therewith

ABSTRACT

A solid electrolyte material comprises Li, T, X and A wherein T is at least one of P, As, Si, Ge, Al, and B; X is one or more halogens or N; A is one or more of S and Se. The solid electrolyte material has peaks at 17.8°±0.75° and 19.2°±0.75° in X-ray diffraction measurement with Cu-Kα(1,2)=1.5418 Å and may include glass ceramic and/or mixed crystalline phases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Nonprovisional applicationSer. No. 16/497,324 filed Sep. 24, 2019 entitled “Solid ElectrolyteMaterial and Solid-State Battery Made Therewith,” which is a 371application of Patent Cooperation Treaty Application No.PCT/US2018/024617 filed Mar. 27, 2018 entitled “Solid ElectrolyteMaterial and Solid-State Battery Made Therewith,” which claims benefitof priority from U.S. Provisional Application No. 62/478,141 filed Mar.29, 2017 entitled “Solid Electrolyte Material and Solid-State BatteryMade Therewith,” all of which are hereby incorporated by reference intheir entirety.

GOVERNMENT RIGHTS

This invention was made with government support under Department ofEnergy Contract Number DE-SC0013236. The government has certain rightsin the invention.

FIELD

Various embodiments described herein relate to the field of solid-stateprimary and secondary electrochemical cells, electrodes and electrodematerials, electrolyte and electrolyte compositions and correspondingmethods of making and using same.

SUMMARY

In an embodiment, a solid electrolyte material comprises Li, T, X and Awherein T is at least one of P, As, Si, Ge, Al, and B; X is a halogen orN; A is one or more of S and Se. The solid electrolyte material haspeaks at 2θ=17.8°±0.75° and 19.2°±0.75° in X-ray diffraction measurementwith Cu-Kα(1,2)=1.5418 Å and may include glass ceramic and/or mixedcrystalline phases.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure may be understood by reference to the followingdetailed description taken in conjunction with the drawings brieflydescribed below. It is noted that, for purposes of illustrative clarity,certain elements in the drawings may not be drawn to scale.

FIG. 1 is a schematic sectional view of an exemplary construction of alithium solid-state electrochemical cell including a solid electrodecomposition, in accordance with an embodiment.

FIG. 2 is a flow chart of a process for producing a solid electrolytecomposition, in accordance with an embodiment.

FIG. 3 is a plot of X-ray diffraction measurements of a solidelectrolyte composition produced by the process indicated in FIG. 2, inaccordance with an embodiment.

FIG. 4 is a plot indicating the improved capacity retention of asolid-state electrochemical cell using a solid electrolyte compositionof the present invention compared to a prior art solid electrolytecomposition, in accordance with an embodiment.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

In the following description, specific details are provided to impart athorough understanding of the various embodiments of the invention. Uponhaving read and understood the specification, claims and drawingshereof, however, those skilled in the art will understand that someembodiments of the invention may be practiced without hewing to some ofthe specific details set forth herein. Moreover, to avoid obscuring theinvention, some well-known methods, processes, devices, and systemsfinding application in the various embodiments described herein are notdisclosed in detail.

The ever-increasing number and diversity of mobile devices, theevolution of hybrid/electric automobiles, and the development ofInternet-of-Things devices is driving greater need for batterytechnologies with improved reliability, capacity (Ah), thermalcharacteristics, lifetime and recharge performance. Currently, althoughlithium solid-state battery technologies offer potential increases insafety, packaging efficiency, and enable new high-energy chemistries,improvements are needed.

FIG. 1 is a schematic sectional view of an exemplary construction of alithium solid-state electrochemical cell including an electrodecomposition of the present invention. Lithium solid-state battery 100includes positive electrode (current collector) 110, positive electrodeactive material layer (cathode) 120, solid electrolyte layer 130,negative electrode active material layer (anode) 140, and negativeelectrode (current collector) 150. Solid electrolyte layer 130 may beformed between positive electrode active material layer 120 and negativeelectrode active material layer 140. Positive electrode 110 electricallycontacts positive electrode active material layer 120, and negativeelectrode 150 electrically contacts negative electrode active materiallayer 140. The solid electrolyte compositions described herein may formportions of positive electrode active material layer 120, negativeelectrode active material layer 140 and solid electrolyte layer 130.

Positive electrode 110 may be formed from materials including, but notlimited to, aluminum, nickel, titanium, stainless steel, or carbon.Similarly, negative electrode 150 may be formed from copper, nickel,stainless steel, or carbon. Negative electrode 150 may be omittedentirely if negative electrode active material 140 possesses adequateelectronic conductivity and mechanical strength. Positive electrodeactive material layer 120 may include, at least, a positive electrodeactive material including, but not limited to, metal oxides, metalphosphates, metal sulfides, sulfur, lithium sulfide, oxygen, or air, andmay further include a solid electrolyte material such as the solidelectrolyte compositions described herein, a conductive material and/ora binder. Examples of the conductive material include, but are notlimited to, carbon (carbon black, graphite, carbon nanotubes, carbonfiber, graphene), metal particles, filaments, or other structures.Examples of the binder include, but are not limited to, polyvinylchloride (PVC) polyanilene, poly(methyl methacrylate) (“PMMA”), nitrilebutadiene rubber (“NBR”), styrene-butadiene rubber (SBR), PVDF, orpolystyrene. Positive electrode active material layer 120 may includesolid electrolyte compositions as described herein at, for example, 5%by volume to 80% by volume. The thickness of positive electrode activematerial layer 120 may be in the range of, for example, 1 □m to 1000 □m.

Negative electrode active material layer 140 may include, at least, anegative electrode active material including, but not limited to,lithium metal, lithium alloys, Si, Sn, graphitic carbon, hard carbon,and may further include a solid electrolyte material such as the solidelectrolyte compositions described herein, a conductive material and/ora binder. Examples of the conductive material may include thosematerials used in the positive electrode material layer. Examples of thebinder may include those materials used in the positive electrodematerial layer. Negative electrode active material layer 140 may includesolid electrolyte compositions as described herein at, for example, 5%by volume to 80% by volume. The thickness of negative electrode activematerial layer 140 may be in the range of, for example, 1 □m to 1000 □m.

Solid electrolyte material included within solid electrolyte layer 130is preferably solid electrolyte compositions as described herein. Solidelectrolyte layer 130 may include solid electrolyte compositions asdescribed herein in the range of 10% by volume to 100% by volume, forexample. Further, solid electrolyte layer 130 may contain a binder orother modifiers. Examples of the binder may include those materials usedin the positive electrode material layer as well as additionalself-healing polymers and poly(ethylene) oxide (PEO). A thickness ofsolid electrolyte layer 130 is preferably in the range of 1 □m to 1000□m.

Although indicated in FIG. 1 as a lamellar structure, it is well knownthat other shapes and configurations of solid-state electrochemicalcells are possible. Most generally, a lithium solid-state battery may beproduced by providing a positive electrode active material layer, asolid electrolyte layer, and a negative electrode active material layersequentially layered and pressed between electrodes and provided with ahousing.

FIG. 2 is a flow chart of a process for producing a solid electrolytecomposition useful for the construction of secondary electrochemicalcells. Process 200 begins with preparation step 210 wherein anypreparation action such as precursor synthesis, purification, andequipment preparation may take place. After any initial preparation,process 200 advances to step 220 wherein sulfur compounds, lithiumcompounds and other compounds, such as described herein, may be combinedwith an appropriate solvent and/or other liquids. Exemplary sulfurcompounds may include, for example, elemental sulfur, phosphoruspentasulfide (P₂S₅), and lithium sulfide (Li₂S) typically in powderforms. Exemplary lithium compounds may include, for example, lithiummetal (Li), lithium sulfide (Li₂S), lithium chloride (LiCl), and lithiumnitride (Li₃N) typically in powder forms. Exemplary solvents mayinclude, for example, but are not limited to, aprotic chain hydrocarbonssuch as heptane, aromatic hydrocarbons such as xylenes, and othersolvents with a low propensity to generate hydrogen sulfide gas incontact with precursors or final electrolyte composition. The solvent isnot particularly limited as long as it remains in the liquid state inpart or in whole during the milling process at the desired millingtemperature and does not participate in deleterious reactions with thesolid electrolyte precursors or final solid electrolyte composition. Theratios and amounts of the various compounds is not specifically limitedas long as the combination permits the synthesis of the desiredcomposition and phase as indicated by the presence of specific X-raydiffraction features. The ratios and amounts may also vary according tospecific synthesis conditions. For example, the ratio of solvent volumeto precursor mass may need to be adjusted as solid electrolytecomposition is adjusted to ensure complete milling of the precursors togenerate the desired solid electrolyte phase discussed herein.

The amount of solvent added to the combination is not limited as long asthe amount supports synthesis of the desired composition of solidelectrolyte material. Multiple solvents may be mixed together with thenoted compounds. Additional materials, such as co-solvents or polymers,may also be added during this step. Furthermore, the synthesis may becarried out with no solvent.

Next, in step 230 the composition may be mixed and/or milled for apredetermined period of time and temperature in order to create a solidelectrolyte as described above. Mixing time is not specifically limitedas long as it allows for appropriate homogenization and reaction ofprecursors to generate the solid electrolyte. Mixing temperature is notspecifically limited as long as it allows for appropriate mixing and isnot so high that a precursor enters the gaseous state. For example,appropriate mixing may be accomplished over 10 minutes to 60 hours andat temperatures from 20 to 120 degrees Celsius. Mixing may beaccomplished using, for example, a planetary ball-milling machine or anattritor mill.

Next, in step 240, the composition may be dried in an inert atmospheresuch as argon or nitrogen or under vacuum for a predetermined period oftime and temperature. Following drying, heat treatment to crystallizethe dried material may be performed during step 250. The temperature ofheat treatment is not particularly limited, as long as the temperatureis equal to or above the crystallization temperature required togenerate the crystalline phase of the present invention. The materialresulting from heat treatment step 250 may be single phase, and may alsocontain other crystalline phases and minor fractions of precursorphases.

Generally, the heat treatment time is not limited as long as the heattreatment time allows production of the desired composition and phase.The time may be preferably in the range of, for example, one minute to24 hours. Further, the heat treatment is preferably conducted in aninert gas atmosphere (e.g., Argon) or under vacuum.

In final step 260, a completed composition may be utilized in theconstruction of electrochemical cells such as the cell of FIG. 1.

Other synthesis routes may be used as well. For example, a methodcomprising the mixing of suitable precursors providing components Li, T,X, and A in a solvent capable of causing reaction between theprecursors, removal of the solvent, and heat treatment at a temperatureequal to or greater than the crystallization temperature of the materialmay be used to synthesize the solid electrolyte material discussedherein.

Example 1

Precursors including 15.5 g Li₂S (Lorad Chemical Corporation), 25.0 gP₂S₅ (Sigma-Aldrich Co.), and 9.5 g LiCl (Sigma-Aldrich Co.), are addedto a 500 ml zirconia milling jar with zirconia milling media andcompatible solvent (e.g. xylenes or heptane). The mixture is milled in aRetsch PM 100 planetary mill for 18 hours at 400 RPM. The material iscollected and dried at 70° C. and then heated to 200° C. in inert (argonor nitrogen) environment. The resulting powder can then be used in apositive electrode active material layer, solid electrolyte layer,and/or negative electrode active material layer.

The sulfide solid electrolyte material resulting from the description ofExample 1 comprises Li, T, X, and A, and has peaks at 17.8°±0.75° and19.2°±0.75° in X-ray diffraction (XRD) measurement withCu-Kα(1,2)=1.5418 Å which identify the novel crystalline phase. T is atleast one kind of P, As, Si, Ge, Al, and B, A is at least one of S andSe, and X is one or more halogens or N. The general chemical compositionmay be denoted as Li_(1-a-b-c-d)P_(a)T_(b)A_(c)X_(d), where values fora, b, c, and d may be in the ranges 0≤a≤0.129, 0≤b≤0.096, 0.316≤c≤0.484,0.012≤d≤0.125, or preferably in the ranges 0.043≤a≤0.119, 0≤b≤0.053,0.343≤c≤0.475, 0.025≤d≤0.125, or more preferably in the ranges0.083≤a≤0.112, 0≤b≤0.011, 0.368≤c≤0.449, 0.051≤d≤0.125. The compositionmay be mixed phase material with other crystalline phases identified byXRD peaks at 2θ=20.2° and 23.6° and/or peaks at 2θ=21.0° and 28.0°,and/or peaks at 17.5° and 18.2°. The compositions may contain acrystalline phase associated with one or more lithium halides.

An exemplary subset of compositions can be defined asLi_(4+3x+u*y-z)P_(1+x-y)T_(y)A_(4+4x-z)M_(1+z) where u is an integerrepresenting the difference in preferred valence state between P and anelement in class T (for example: P⁵⁺—Al³⁺=2), and T and A representelements as described herein, and M is a halogen. Compositions may be inthe range of 0≤x≤4, 0≤y≤4, 0≤z≤7, or preferably 0≤x≤3, 0≤y≤1, 0≤z≤2, ormore preferably 1≤x≤3, 0≤y≤0.5, 0≤z≤1.

An exemplary composition is defined by x=1, y=z=u=0, A=S, and M=Cl inLi_(4+3x+u*y-z) P_(1+x-y)T_(y)A_(4+4x-z)M_(1+z). Such a composition,after heat treatment, yields the crystalline phase of the presentinvention. The structure of this crystalline phase is conducive to highionic conductivity, and the presence of halogens may aid in theformation of stable, low-resistance interfaces against lithium metal andhigh voltage cathode active materials.

FIG. 3 is a plot of X-ray diffraction measurements of a solidelectrolyte composition produced by the process indicated in FIG. 2according to Example 1. X-ray diffraction (XRD) measurements showdominant novel peaks indicative of a previously unknown crystallinephase at 17.8°±0.75° and 19.2°±0.75° with Cu-Kα(1,2)=1.5418 Å. Othercompositions may be mixed phase material with other crystalline phasesidentified by XRD peaks at 2θ=20.2° and 23.6° and/or peaks at 2θ=21.0°and 28.0°, and/or peaks at 17.5° and 18.2°, and/or peaks associated withone of more lithium halides.

FIG. 4 is a plot indicating the improved capacity retention duringcycling of solid-state electrochemical cells using a solid electrolytecomposition of the present invention compared to a prior art solidelectrolyte composition. Further studies of the compositions describedherein indicate that the compositions including the novel phase deliverimproved resistance and capacity stability at elevated temperatures andcharge cutoff voltages. The electrolyte composition may also havemechanical properties conducive to improved physical contact andcoverage of the cathode active material as evidenced by cathode capacityutilization near 100% during cycling. Measured examples of thecompositions provide conductivities of approximately 0.6-2 mS/cm at roomtemperature for pure and mixed-phase electrolyte material in pelletscompressed at room temperature. Higher conductivities may possibly beattained by an altered chemical stoichiometry and/or by compression atelevated temperatures or other processing methods and conditions.

Features described above as well as those claimed below may be combinedin various ways without departing from the scope hereof. It should thusbe noted that the matter contained in the above description or shown inthe accompanying drawings should be interpreted as illustrative and notin a limiting sense. The above-described embodiments should beconsidered as examples of the present invention, rather than as limitingthe scope of the invention. In addition to the foregoing embodiments ofinventions, review of the detailed description and accompanying drawingswill show that there are other embodiments of such inventions.Accordingly, many combinations, permutations, variations andmodifications of the foregoing embodiments of inventions not set forthexplicitly herein will nevertheless fall within the scope of suchinventions. The following claims are intended to cover generic andspecific features described herein, as well as all statements of thescope of the present method and system, which, as a matter of language,might be said to fall there between.

What is claimed is:
 1. A solid electrolyte material comprising: Li, T, Xand A wherein T is at least one element selected from the groupconsisting of P, As, Si, Ge, Al, and B; X is one or more halogens or N;A is one or more of S and Se; and the solid electrolyte material haspeaks at 17.8°±0.75° and 19.2°±0.75° in X-ray diffraction measurementwith Cu-Kα(1,2)=1.5418 Å.
 2. The solid electrolyte material of claim 1,wherein the composition may be described by the general formula:Li_(1-a-b-c-d)P_(a)T_(b)A_(c)X_(d) in which 0≤a≤0.129, 0≤b≤0.096,0.316≤c≤0.484, 0.012≤d≤0.125.
 3. The solid electrolyte material of claim2, wherein a=0.111, b=0, c=0.444, d=0.056, A=S, and X=Cl.
 4. The solidelectrolyte material of claim 1, further comprising at least one ofglass ceramic phases, crystalline phases and mixed phases.
 5. The solidelectrolyte material of claim 1, wherein mixed phases comprisecrystalline phases containing peaks at 20.2°±0.75° and 23.6°±0.75°,and/or 21.0°±0.75° and 28.0°±0.75°, and/or 17.5°±0.75° and 18.2°±0.75°in X-ray diffraction measurement with Cu-Kα(1,2)=1.5418 Å.
 6. The solidelectrolyte material of claim 5, wherein a ratio of peak intensity at19.2°±0.75° to a peak at 17.5°±0.75° is 1 or more.
 7. A lithiumsolid-state battery comprising a positive electrode active materiallayer containing a positive electrode active material; a negativeelectrode active material layer containing a negative electrode activematerial; and a solid electrolyte layer disposed between the positiveelectrode active material layer and the negative electrode activematerial layer, wherein at least one of the positive electrode activematerial layer, the negative electrode active material layer, and thesolid electrolyte layer comprises the solid electrolyte materialaccording to claim
 1. 8. A method for producing a sulfide solidelectrolyte material including glass ceramics comprising: Li, T, X and Awherein T is at least one of P, As, Si, Ge, Al, and B; X is one or morehalogens or N; A is one or more of S and Se; the method comprisingmixing and milling a raw material composition containing an element A orcompound Li₂A, an element T or sulfide of T, and a compound LiX or Li₃Nto render the mixture amorphous under x-ray diffraction; and heating thesulfide glass at a heat treatment temperature equal to or greater than acrystallization temperature of the sulfide glass to synthesize the glassceramics having peaks at 17.8°±0.75° and 19.2°±0.75° in X-raydiffraction measurement with Cu-Kα(1,2)=1.5418 Å.